Discovery of lysosome-targeted covalent anticancer agents based on isosteviol skeleton

Covalent drugs play corresponding bioactivities by forming covalent bonds with the target, which possess many significant pharmacological advantages including high potency, ligand efficiency, and long-lasting effects. However, development of covalent inhibitors is a challenge due to their presumed indiscriminate reactivity. Here, we report the discovery of series of lysosome-targeting covalent anticancer agents by introducing nitrogenous bases to the modified isosteviol skeleton in order to minimize the toxicity and increase the selectivity. By introducing the electrophilic α, β-unsaturated ketones into the A- and D-rings of isosteviol, the cytotoxicity of the obtained compounds were greatly increased. Further nitrogen-containing modifications to the D-ring led to the discovery of novel molecules that targeted lysosomes, and of which, compound 30 was the most potent and selective antiproliferative one to kill A549 cells in vitro and in vivo. Mechanism investigation revealed that compound 30 was trapped into lysosomes and damaged lysosomes to cause cell death.